Abstract
The two-pore domain K2P subunits form background (leak) potassium channels, which are characterized by constitutive, although not necessarily constant activity, at all membrane potential values. Among the fifteen pore-forming K2P subunits encoded by the KCNK genes, the three members of the TREK subfamily, TREK-1, TREK-2, and TRAAK are mechanosensitive ion channels. Mechanically induced opening of these channels generally results in outward K+ current under physiological conditions, with consequent hyperpolarization and inhibition of membrane potential-dependent cellular functions. In the past decade, great advances have been made in the investigation of the molecular determinants of mechanosensation, and members of the TREK subfamily have emerged among the best-understood examples of mammalian ion channels directly influenced by the tension of the phospholipid bilayer. In parallel, the crucial contribution of mechano-gated TREK channels to the regulation of membrane potential in several cell types has been reported. In this review, we summarize the general principles underlying the mechanical activation of K2P channels, and focus on the physiological roles of mechanically induced hyperpolarization.
Highlights
The two-pore domain (K2P ) potassium channels are the molecular correlates of background potassium currents, which mediate K+ transport through the plasma membrane, regulate the value of the membrane potential, and adjust cellular excitability [1].The different K2P channel types are characterized by similar membrane topology, molecular architecture, and overall electrophysiological properties
The pore selectivity filter (narrow rectangle close to the space, and the chain vertically returns to the EC side as the (TVGYG-like) signature sequence of helix and the signature sequence belong to the first pore domain, as illustrated in panel A
It has been reported that TREK-1 and TRAAK mRNA and protein are expressed in the rodent and human myometrium [121,122,123,124]
Summary
The two-pore domain (K2P ) potassium channels are the molecular correlates of background (leak) potassium currents, which mediate K+ transport through the plasma membrane, regulate the value of the membrane potential, and adjust cellular excitability [1]. One subunit orange loops are red) and the otherisisfollowed blue, andby the α-helical regions are illustrated as tubes.isThe first(pore transmembrane segment (TM1). The pore selectivity filter (narrow rectangle close to the space, and the chain vertically returns to the EC side as the (TVGYG-like) signature sequence of helix and the signature sequence belong to the first pore domain, as illustrated in panel A. The pore acid chain continues as the (not entirely straight) TM2 and TM3 transmembrane helices, followed helix and the signature sequence belong to the first pore domain, as illustrated in panel A. The narrow selectivity filter region of the transmembrane pore is compared to panel B, the cap helices of the two subunits almost overlap in the illustration. Homodimer rotated bycavity), about aby quarter compared to by a large onecentral
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